feat!: remove deprecated command-line option -platform-user

[knst]

Issue being fixed or feature implemented

This command-line option has never been used for platform, marked as deprecated in v22. Time to remove it.

What was done?

Removed deprecated command line option -platform-user and related code

How Has This Been Tested?

Breaking Changes

Removed deprecated command line option -platform-user and related code

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone (for repository code-owners and collaborators only)